Substrate handling system for aligning and orienting substrates during a transfer operation

ABSTRACT

A system is provided for sensing, orienting, and transporting wafers in an automated wafer handling process that reduces the generation of particles and contamination so that the wafer yield is increased. The system includes a robotic arm for moving a wafer from one station to a destination station, and an end-effector connected to an end of the robotic arm for receiving the wafer. The end-effector includes a mechanism for gripping the wafer, a direct drive motor for rotating the wafer gripping mechanism, and at least one sensor for sensing the location and orientation of the wafer. A control processor is provided for calculating the location of the center and the notch of the wafer based on measurements by the sensor(s). Then, the control processor generates an alignment signal for rotating the wafer gripping mechanism so that the wafer is oriented at a predetermined position on the end-effector while the robotic arm is moving to another station.

This is a continuation from co-pending International Patent ApplicationNo. US03/28391, filed Sep. 10, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The exemplary embodiments of the present invention relate to a substratetransport system and, more particularly, to a substrate transport systemcapable of orienting and aligning a substrate “on the fly”.

2. Brief Description of Earlier Related Developments

In semiconductor fabrication processes, wafers are transferred betweenstations, such as storage, queuing, processing and other work stations.In typical automated wafer handling processes, a wafer is first pickedup by a robotic arm for transfer from one station to another station.Next, the wafer is placed on an aligner for aligning and centering thewafer to a desired position using a notch or flat located on the wafer'sedge. Once properly aligned, the wafer is then placed in the desiredstation for processing. After the processing is completed at the desiredstation, the wafer may then be picked up and placed again at anotherstation.

Each time that the wafer is picked up, placed, and aligned, contact ismade with either the edge or the back side of the wafer and particlesare generated. For instance, in a single wafer process cycle, the wafermay be contacted as many as twelve times when using a three-axis aligneror at least eight times when a single axis aligner is used.

In addition, the alignment process requires a dedicated aligning deviceand a separate step in the wafer process cycle. The dedicated aligningdevice often creates a bottleneck that limits the wafer throughput inthe system and also introduces additional handling that generatesparticles. Adding aligners to the system may help to slightly increasethis throughput problem but creates an undesirable increase in the cost,complexity and generation of particles to the wafer handling system.Accordingly, a system is desired for enhancing the wafer handlingprocess by reducing the generation of particles and wafer damage so thatthe wafer yield is increased. Also, it is desired to increase the waferthroughput by performing the alignment process in parallel with movingthe wafer.

In order to effect alignment/reorienting of the wafer (or any other flatpanel substrate/workpiece) in parallel with moving the wafer so called“on the fly” alignment, the handling systems are generally provided withmeans or drives for performing such alignment. In conventional handlingsystem, the “on the fly” alignment drives have generally been used bysystems that do not employ “edge gripping” for holding the substrate.These non-edge gripping systems, however, are generally falling intodisfavor with users (for edge-gripping systems) because the non-edgegripping systems contact the wafer surface with the associated potentialfor contamination. In the case of edge gripping systems, attempts havebeen made to provide an “on the fly” alignment drive. These conventionalattempts take the form of a servomotor mounted away from the wafer andthe chuck holding the wafer on the handling system. This is known as“off axis” mounting. The servomotor is connected to the chuck by asuitable transmission that imparts motion from the servomotor to thechuck. In conventional systems, locating the motor away from thesubstrate minimizes potential for particulate contaminants generatedduring motor operation coming in contact with the wafer surfaces.Nevertheless, by employing a transmission to connect the motor to thechuck, such as cables, conventional systems still have the potential forhaving particles contaminate the surface of the wafers being handled.Further, the transmission, by its very nature as a further drive elementbetween motor and chuck, increases the possibility for inaccuracy inplacement/aligning of the substrate. The transmission further increasesthe weight and complexity of the end effector with a detrimental impactto the control of the handling system. Further, due to the very tightheight constraints, the chuck, of the end effector is inserted betweenstacked wafers in a pod/cassette with a pitch of about 10.0 mm and awafer thickness of about 0.77 mm, the transmission design is complex.Correspondingly, the transmission may be unreliable and time consumingto install. The present invention as evident from the exemplaryembodiments overcomes the problems of conventional handling systems aswill be described in greater detail below.

SUMMARY OF THE EXEMPLARY EMBODIMENTS

The present invention is directed to a system for locating and orientingsubstrates, such as semiconductor wafers, during the pick up andtransfer steps in an automated substrate handling process. In asemiconductor fabrication process, the system is able to reduce thegeneration of particles from and the contamination of semiconductorwafers. As a result, the wafer yield and throughput of the fabricationprocess are increased.

More particularly, the system includes a robotic arm for moving a waferfrom one station to another station. An end-effector is connected to anend of the robotic arm for handling the wafer. The end-effector mayinclude a mechanism for gripping the wafer, a mechanism, such as amotor, for moving the wafer gripping mechanism, and at least one sensorysystem for sensing the location and orientation of the wafer. A controlprocessor operatively connected to the robotic arm and the end-effectorcalculates the location of the center and a notch or flat of the waferbased on data from the at least one sensory system. The controlprocessor generates a signal to move the wafer gripping mechanism sothat the wafer is centered on the end-effector when picked by theend-effector and is oriented at a predetermined position on theend-effector while the robotic arm is moving to another station. Afterthe wafer is picked up by the end-effector, the control processor canrefine the calculation of the center of the wafer and adjust the wafer'sorientation before being dropped off at the next station.

Other aspects, features and advantages of the present invention aredisclosed in the detailed description of the exemplary embodiments thatfollows.

DESCRIPTION OF THE DRAWINGS

The exemplary embodiments will be more fully understood by reference tothe following detailed description of the invention in conjunction withthe drawings, of which:

FIG. 1 illustrates a block diagram of a wafer handling system accordingto an embodiment of the present invention;

FIG. 2 illustrates a robotic arm and an end-effector used in a waferhandling system according to an embodiment of the present invention;

FIG. 3 illustrates exemplary wafer positioning measurements according toan embodiment of the present invention;

FIG. 4 illustrates an example of a voltage output curve from acapacitive sensor that may be used for sensing wafer edges;

FIG. 5 illustrates a wafer notch measurement according to an embodimentof the present invention;

FIG. 6 illustrates a sensor configuration on an end-effector accordingto an embodiment of the present invention;

FIG. 7 illustrates a detailed view of an end-effector according to anembodiment of the present invention

FIG. 8 is a perspective view of an end-effector according to anotherembodiment of the present invention;

FIG. 9 is a plan view of the end-effector in FIG. 8 and a substrate S;

FIG. 9A is a cross-section view of the end-effector and substrate Staken along view line A-A in FIG. 9;

FIG. 9B is an enlarged partial cross-section view of the end effectorand substrate S in FIG. 9B;

FIG. 10 is an exploded perspective view of the end effector in FIG. 8;

FIG. 11 is another perspective view of the end effector in FIG. 8 withthe chuck of the end effector rotated to a different position from thatshown in FIG. 8; and

FIG. 12 is a plan view of a stator and rotor of a motor of the endeffector shown in FIG. 8.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

A substrate handling system according to the present invention providesa robotic arm configured to handle substrates, such as semiconductorwafers, reticles, etc. The system is operative to sense the substrateand center the substrate with respect to the robotic arm's end-effectorprior to picking up the substrate. The system is also operative toorient the substrate in a desired orientation and to calculate thecenter of the wafer during transfer of the substrate to a destinationstation. The system is particularly useful in transferring semiconductorwafers between stations in a semiconductor fabrication process. Thesystem reduces the amount of wafer handling necessary between stationsso that the generation of particles from and contamination of the wafersdecreases, increasing wafer yield. The system eliminates a separatealignment step, thereby increasing wafer throughput.

Referring to FIG. 1, the system includes one or more robotic armassemblies 20 operatively communicative with a control processor 10 by,for example, a bus, cable or wireless connection 12. Each of the roboticarm assemblies 20 includes an end-effector 40 operatively communicativewith the control processor 10 by a bus, cable or wireless connection 14,which will be described in more detail below, and is associated with oneor more stations 30, 32 and 34 for moving substrates, such as wafers,therebetween. The end-effector 40 includes a substrate gripper ormechanism 42 and a sensory system 44. The control processor 10calculates the location of the center and an alignment feature, such asa notch or flat of the wafer, based on data from sensors on theend-effector and generates centering, aligning, and orienting signalsfor the end-effector based on these calculations. The control processor10 computes and communicates to the robotic arm assemblies 20 the actualsubstrate center position, and the arm assembly positions theend-effector 40 centered relative to the substrate before gripping thesubstrate.

After the end-effector 40 grips the centered wafer, the controlprocessor 10 generates additional signals for rotating the wafer andprocessing the sensor signals in order to finally re-compute the wafercenter, find the notch or flat position and rotate the notch or flat ina desired position. The orientation, alignment and robotic armtrajectory correction are performed while the robotic arm moves thewafer from one station to another station. The control processor 10 mayinclude distributed control architecture for performing the orientation,alignment and correction. The control processor 10 may also be mountedin close proximity to the end-effector 40 for independently controllingthe alignment feature.

FIG. 2 schematically illustrates a typical robotic arm assembly 100 formoving a semiconductor wafer 102 from one station to another station inthe semiconductor fabrication process. The arm assembly 100 includes anarm 120 mounted on a support 110, such as a central column that houses alifting mechanism (not shown) to raise and lower the arm vertically. Thearm 120 includes an inner arm 122, an outer arm 124, and theend-effector 130. The inner arm 122 is supported by the central column110 at a rotatable “shoulder” joint 126 to effect rotation about avertical axis through the central column 110. Similarly, the outer arm124 is mounted to the inner arm 122 at a rotatable “elbow” joint 128 forrotation about a vertical axis, and the end-effector 130 is mounted tothe outer arm 124 at a rotatable “wrist” joint 132 for rotation about avertical axis. Rotation about the three rotatable joints 126, 128 and132 allows the end-effector 130 to move to any coordinate position in ahorizontal plane, while translation of the arm 120 on the central columnprovides vertical motion. It will be appreciated that the presentinvention can be used with other robotic arm configurations.

The end-effector 130 includes a wafer gripping mechanism 134, such as avacuum wafer chuck, for gripping the wafer 102. It is appreciated thatedge grippers and other known wafer handling mechanisms may also beused. A motor 136 or other suitable mechanism is provided for rotatingthe wafer gripping mechanism 134 when orientation is required. One ormore sensors 138 are mounted at fixed and known locations on theend-effector 130 to sense the location and notch orientation of thewafer 102 with respect to the end-effector 130, described further below.Data collected by the sensors 138 is communicated to the controlprocessor 10, which calculates the center of the wafer 102 and thelocation of its notch or flat before the wafer 102 is gripped by thewafer gripping mechanism 134. With the location data from the sensors138, the known center of the end-effector 130 is positioned underneaththe calculated center of the wafer 102, the end-effector 130 is raiseduntil the wafer gripping mechanism 134 contacts the underside of thewafer 102, and the wafer gripping mechanism 134 is actuated to grip thewafer 102. Once the wafer 102 is gripped, the robotic arm assembly 100moves the wafer 102 towards the next station. At the same time, theend-effector 130 aligns the wafer 102 by rotating the wafer grippingmechanism 134 to place-the notch or flat of the wafer 102 in its desiredorientation prior to releasing the wafer 102 at the next station.

The control processor 10 is able to calculate the location of thewafer's center W_(c) based on the sensor data. See FIG. 3. The diameterof the wafer 102 is known. Commonly in semiconductor fabrication, thewafers have a diameter of 300 mm. As noted above, the locations of thesensors 138 are fixed with respect to the end-effector 130 and are thusknown by the control processor 10. Thus, the center of the wafer 102 canbe determined by sensing at least two edge locations of the wafer 102,from which a chord length can be calculated. Note that, if the sensors138 are located near the leading edge of the end-effector 130, that is,the edge of the end-effector 130 that first moves underneath the wafer102, the control processor 10 can be instructed that the center of thewafer 102 is in front of the leading edge. Thus, two edge data pointsare sufficient to enable the calculation of the location of the centerof the wafer 102 of known diameter. The control processor 10 is thenable to move the end-effector 130 to a desired alignment with respect tothe wafer 102, for example, with the wafer center W_(c) over a centerE_(c) or other desired point of the end-effector 130.

Preferably, at least two sensors are placed at known locations on theend-effector to sense at least two wafer edge locations. It will beappreciated, however, that a single sensor on-the end-effector can beused if the sensor is suitably moved to sense two or more separate edgelocations on a wafer. It will also be appreciated that a greater numberof sensors can be used to provide a greater number of data points. Ifmore than two data points are used, an average of the calculated centerpoints can be determined.

The sensors 138 can be of any suitable type, such as capacitive,optical, acoustic, or ultrasonic sensors. As an example, if a capacitivesensor is used, the capacitance increases as the sensor moves underneatha wafer. For each sensor, a voltage output, which is proportional toimpedance, is generated to select an appropriate edge point, indicated,as an example, by a vertical dashed line on FIG. 4. The actual edgepoint selected for use in the subsequent calculations is determined by aset of real time measurements and voltage/distance curves. The dataprocessing algorithm can use look-up tables, statistical inference, orartificial intelligence, as would be known by one of skill in the art.

The detected capacitance is also dependent on the distance from thesensors to the bottom surface of the wafer. This distance can vary ifthe wafer is, for example, warped or tilted within the storagecontainer. Thus, a sensor to detect this distance is preferablyprovided. This sensor is located to pass underneath the wafer in advanceof the edge-detecting sensor. In this manner, the distance to the wafercan be provided, which enables a better determination of the edge to bemade. For example, a calibration curve or look-up table can be providedfor the appropriate distance from the wafer. Also, if the wafer iswarped or tilted, the wafer may not be gripped correctly. Typically, ifthe wafer is not gripped correctly, the wafer gripping device ungripsand regrips or it aborts the grip and reports an error. Thus, thedistance sensors can be used to determine if warping or a tilted waferis present and to improve the robustness of the system.

Once the end-effector 130 is in alignment with the wafer 102, theend-effector 130 is raised vertically until it contacts the wafer 102.The wafer gripping mechanism 134 is engaged to grip the wafer 102. Forexample, if the wafer gripping mechanism 134 is a vacuum chuck, thechuck is actuated to draw the underside of the wafer 102 to the chuck.The robotic arm assembly 100 then begins the transfer of the wafer 102to the next station. During this transfer, the wafer gripping mechanism134 may be rotated until the notch or flat of the wafer 102 is detectedby one of the sensors 138 located on the end-effector 130 for purposesof detecting the notch. Once the notch is detected, the wafer grippingmechanism 134 is rotated until the notch is located in the desiredorientation for placement at the destination station.

The notch may be detected in any suitable manner. For example, using acapacitive sensor, the capacitance decreases when the notch overlays thesensor, which may appear as a spike in a voltage/distance curve. Asshown in FIG. 5, when the notch 104 is positioned over one of thecapacitive sensors 138, the value measured by the sensor decreases, andwhen the notch 104 is not positioned over any of the sensors 138, thevalue measured by the sensor increases. In this example, a small sizedsensor is preferred to increase the resolution of capacitive varianceand enhance the accuracy in detecting the notch. Based on iterations ofthese calculations and comparisons, the position of the notch 104 on thewafer 102 may be determined. Once the notch 104 is detected, the wafer102 may be oriented in the desired position. The control processor 10may also make further adjustments to the orientation of the wafer 102during the placing step when the end-effector 130 approaches thedestination station. For example, knowing the location of the center ofthe wafer 102 with respect to the end-effector 130, the controlprocessor 10 can move the end-effector 130 as necessary to deposit thewafer 102 in a desired position at the destination station.

The system may also include a teach process for improving the truelocation of the stations when the system is initially configured andwhenever a system component is changed, such as an aligner, POD door orstage, for instance. In the teach process, the sensors 138 are firstmoved under or over a datum plate or a locating feature (there may bemultiple locating features) positioned at known coordinates within thesystem. The data from the sensors 138 are used to provide feedback onwhether the robotic arm assembly 100,is level and its absolute positionin the global coordinate system. The robotic arm assembly 100 isadjusted if the data suggests that it is not level.

Next, the robotic arm assembly 100 moves to each work station 30, 32,and 34. As the leading edge of the substrate is detected, the center ofthe substrate is calculated. This information is used as the new stationlocation. Additionally, information is provided on whether the stationis level by measuring the apparent distance from the substrate as thesensors move under or over the substrate. With this information, a usermay manually adjust and level the station. These steps are repeated forall of the work stations. This information may be also used to measuresystem changes and to predict failures. This teach process may beperformed to improve the true locations of a full end-aligner orend-effectors with sensors.

FIG. 6 illustrates an embodiment of the present invention in which sixsensors 150, 152, 154, 160, 162 and 164 are placed at predeterminedlocations around the periphery of an end-effector base 170. In thisembodiment, three rectangular sensors 150, 152 and 154 are used forsensing the edge of the wafer 102 and three circular sensors 160, 162and 164 are used for sensing the notch and the distance of the wafer 102from the end-effector base 170. The sensors 150, 152, 154, 160, 162 and164 may be capacitive, acoustic, optical, reflective or other types ofknown sensors. This configuration of sensors allows the robotic arm topick up the wafer and to grip the wafer without having the wafer slipalong the surface of the wafer gripping mechanism or during placement inthe station. The motion of the end-effector base 170 as it passes underthe wafer 102 is used to detect the presence of the front and rearpositions of the wafer 102. These measurements in combination with thegeometry of the wafer (the diameter of the wafer) are used to determinethe wafer's center and to adjust the pickup position in conjunction withgeometric distance calculation algorithms. These measurements may alsobe used for controlling edge grippers to eliminate sliding or in caseswhere orientation of the notch is not required.

Although six sensors are used in the embodiment of FIG. 6, additionalsensors and types of sensors may be used to increase the accuracy forcalculating the center and compensating for errors such as a warpedwafer, notches passing under the sensors and differences in substratesizes. Generally, a straight motion by the end-effector under the waferis used for pick up. However, other non-linear motions may be used togather additional data points based on the number of sensors, and thesize and-shape of the substrate in conjunction with the motion. Suchalternative motions may reduce the number of necessary sensors to aslittle as one sensor.

The end-effector, with its edge gripping mechanism, motor and sensors,must be sufficiently thin to fit between wafers stored in a stack.Typically, the distance between wafers in a stack is 10 mm of pitch and0.77 mm of wafer thickness. FIG. 7 illustrates an embodiment of anend-effector 200 according to the present invention suitable for usewith a stack of wafers with a small distance between the wafers. Theend-effector 200 includes an end-effector base 202 that is connected tothe robotic arm (not shown in this figure) at a connecting portion 204thereof. The end-effector base 202 includes a first circular ledge 208for receiving a motor stator 210 therein. The inner race 228 of themotor, such as a contact bearing, is seated on the end-effector base202, that circularly extends up and around from the middle of theend-effector base 202. A motor rotor 214 and an encoder disk 216 arefirst disposed on the back surface of a wafer chuck 222. Then, the waferchuck 222 with the motor rotor 214 and the encoder disk 216 together fiton the outer race of the contact bearing 212. After this fit, a gapbetween the encoder read head 218 and the encoder disk 216 is realized.Typically, the resulting gap is approximately 1 to 2 mm. An opening 224at the center of the end-effector base 202 is connected to a vacuumchannel (not shown). A ring seal 226 is disposed between the opening 224of the end-effector base 202 and the bottom surface of the wafer chuck222 for applying a vacuum across the top surface of the wafer chuck 222to grip the wafers.

The end-effector base 202 further includes openings 230, 232, 234 and236 for receiving sensors 240, 242, 244 and 246 that are positionedaround the outer peripheral portion of the end-effector base 202. Theopenings 230, 232, 234 and 236 may be circular, rectangular, ellipticalor other shapes and are dependent upon the designs of the sensors 240,2.42, 244 and 246 that are being used for the sensing application. Thesensors 240, 242, 244 and 246 may be capacitive, acoustical, optical,reflective or other known types of sensors for sensing applications suchas determining the presence, absence and height of the wafer above thebase, for example. To maximize the detection resolution, a plurality ofsensors are positioned around the base and the surface area of eachindividual sensor is made as small as possible while still being largeenough to detect edges and surfaces. Also, rectangular shaped sensorsare preferred to detect wafer edges and circular shaped sensors todetect the distance of the wafer from the sensor in addition to edgesand the notch of the wafer. However, it should be realized thatdifferent sensor shapes and sizes may be used depending upon the desiredsensing application and resolution.

In the embodiment of FIG. 7, three circular sensors 240, 242 and 244 andone rectangular sensor 246 are positioned around the periphery of theend-effector base 202. Two of the circular sensors 240 and 242 arepositioned towards the front the end-effector base 202 (typically theportion that first reaches the wafer) for first sensing wafer edges. Theother circular sensor 244 and the rectangular sensor 246 are positionednear the periphery of the end-effector base 202 that connects to therobotic arm. Measurements from the rectangular sensor 246 and the twofront sensors 240 and 242 are sent to the control processor and are usedto center the wafer on the wafer chuck 222. Measurements from the threecircular sensors 240, 242 and 244 are also used to align the planes ofthe wafer chuck 222 and the underside of the wafer. Once the wafer iscentered and aligned, the vacuum is applied to the wafer chuck 222 andthe wafer is gripped.

The robotic arm then moves the wafer to another station. While therobotic arm is moving, one of the three circular sensors-.240, 242 and244 is used to detect the notch. The three circular sensors 240, 242 and244 are positioned so that the edge of the wafer passes substantiallythrough the middle of each sensor. Once one of the sensors detects thatthe notch is directly over it, the control processor may then generateorienting signals to the end-effector 200 so that the notch ispositioned at the desired orientations. This orientation is typicallycompleted during the time that it takes for the wafer to reach thedestination station.

The present system centers the wafer on the wafer gripping mechanism andpositions the notch or flat in the desired orientation while moving thewafer from one station to a destination station without the need for aseparate aligning or centering device. Because impacts between the waferand the end-effector or the wafer and a cassette or stand generateparticles that may damage the wafer, the present invention desirablyminimizes picking up and placing of the wafers during the handlingprocess. By eliminating an aligning device, at least one pick up andplacing step is eliminated in the processing for each wafer. As aresult, the wafer throughput is greatly improved since the alignment isdone in parallel with the motion of the robotic arm, which reduces bothprocessing time and equipment costs. For instance, if a cassette of 25wafers is processed, a considerable amount of time can be saved inaddition to improving the reliability of the system while drasticallyreducing particle generation to improve wafer yield.

Referring now to FIG. 8 there is shown a perspective view of an endeffector 300 in accordance with another exemplary embodiment of thepresent invention. End effector 300 is generally similar to the otherend effectors 130, 200 described before and shown in FIGS. 2, 6 and 7.As with the other end effectors, end effector 300 can be mounted (at ajoint similar to wrist joint 132) to the arm assembly 100 (See FIG. 2)in a substantially similar manner as end effectors 130, 200. Referringalso to FIG. 10, which shows an exploded perspective view, the endeffector 300 generally comprises a base 302, a chuck 322, and a motor309. The base 302 is generally configured to allow the end effector tobe mounted for example to the wrist joint 132 of the transfer arm 100(see FIG. 2) as described above. The chuck 322 is movably supported fromthe base 302. The chuck 322 has structures for holding a substrate S(see for example FIG. 9) by edge gripping the substrate. As notedbefore, substrate S (similar to substrate 102 in FIG. 2) may be anysuitable type of flat panel, such as a semiconductor wafer, a reticle, aflat panel display, and is shown as having a substantially circularoutline for example purposes only. The motor 309 is also supported bythe base 302 and is connected to the chuck to move the chuck 322relative to the base. The motor 309 is located under the chuck and hasan axis of motion R extending substantially through the center C of thesubstrate S when the substrate is held by the chuck 322. The motor 309is a brushless motor integral to the base and chuck, and is controlledby controller 10 (see FIG. 1). The end effector 300 also includes apositional resolver 316 that is communicably connected to the controller10. Sensors in the end effector, similar to the sensors in end effector200, locate a fiducial on the substrate S from which the controller 10finds the current orientation of the substrate and determines thedesired orientation. The motor 309, under command from the controller10, moves the chuck 322 until the desired orientation is achieved.

In greater detail now, and with reference also to FIGS. 9, 9A-9B whichrespectively show a plan view, a cross-sectional view through view lineA-A, and an enlarged partial cross-sectional view of the end effector300 and substrate S, the base 302 of the end effector generallycomprises a rear section 302R (shown in phantom in FIG. 8), and a frontsection 302F. The rear section 302R has fixtures and attachments (notshown) possibly similar to base sections 130, 202 for mounting the base302., and hence the end effector 300 to the arm. The front section 302Fof the base 302 extends from the rear section 302R. The front section302F in this embodiment forms the front 307 (i.e. the portion insertedto pick/place substrate S) of the end effector 300 (see FIG. 9). Thefront section 302F of the end effector may be a one-piece member (i.e.of unitary construction). In this embodiment, the front section 302F ofthe base is a printed circuit board (PCB). As seen in FIG. 9B, the PCBis self supporting and forms the structure of the front section 302F ofthe base. As can be realized from FIGS. 9 and 9A, the PCB forming thefront section supports the chuck 322 of the end effector, and thesubstrate S held by the chuck. In alternate embodiments, the front andrear sections of the base may be included in a one-piece member PCB. Inthat case, a portion of the PCB itself may provide the attachments formounting the end effector to the transport arm. In other alternateembodiments, the front section of the base may be an assembly thatincludes a PCB section supporting the chuck.

As can be realized from FIGS. 9 and 9B, the PCB forming the frontsection 302F (the front section will be referred to hereinafter as thePCB section of the base) is sized so that the stack height of the endeffector 300 can be admitted between substrates having a 10.0 mm pitch.Accordingly, the board material of the PCB may have high stiffness tominimize undesired deflections of the base. The board material may befor example Alumina ceramic, carbon fiber composite, or any othersuitable ceramic, composite, or plastic material having suitableinsulating and mechanical properties to form the board of the PCB. Asseen in FIG. 10, the stator 310 of motor 309 is formed in the PCBsection 302F. In this embodiment, motor 309 is a rotary motor, though inalternate embodiments the end effector may incorporate a linear orplanar motor in a manner substantially similar to that described below.As seen in FIG. 10, the stator 310 may have a generally circularconfiguration. The stator 310 may be formed integrally with the PCBsection, by cladding the PCB during PCB fabrication as desired to definethe windings of the stator. Any suitable cladding process may be usedsuch as a lithographic process forming a desired number of layers on thePCB to generate the windings. The windings may be formed of any suitableconductive material such as copper, or tungsten. FIG. 12 shows a planview of the stator windings 310A-310C formed integral to the PCB. Theconfiguration of the windings 310A-310C shown in FIG. 12 is exemplary,and the windings may be formed to have any suitable configuration. Thewindings 310A-310C are disposed in the PCB to generate a magnetic fieldoriented axially across the stator. In alternate embodiments, thewindings of the stator may be configured to generate a magnetic fieldhaving any other desired orientation. The stator windings are arrangedin three phases 310A-310C as shown in FIG. 12, though in alternateembodiments the stator windings may have any suitable number of phases.In this embodiment, the stator is shown as having (for example purposes)nine winding coils (three for each phase) though any suitable size andnumber of winding coils may be used. The PCB section 302F may furtherhave formed therein suitable conductive traces connecting the windingsto a suitable power source (not shown) and to the controller 10 (seeFIG. 1). The controller 10 controls the commutation of the statorwindings 310A-310C as will be described further below to effectoperation of the motor 309.

As seen best in FIGS. 9A-9B, and 12, the PCB section 302F has a recess308 formed therein. The recess 308 in the PCB section 302F has agenerally circular shape, and is substantially concentric with theintegral stator 310 formed in the PCB section. The recess 308 providessupport and coupling for the chuck 322 to the base 302 of the endeffector. The recess 308 may have a deeper, substantially annular outerportion 306, and a more shallow inner portion 307. The outer portion 306forms a radial seating surface 306R and a horizontal seating surface306H. The radial surface 306R may be sized to form a close or press fitwith the outer face of the very low profile bearing 312 used forrotatably coupling the chuck 322 to the base of the end effector. Asnoted before, the concentric configuration of the recess 308, and henceof radial surface 306R, with the stator results in the bearing 312 beingconcentric with stator 310 when the bearing is placed in recess 306. Thehorizontal seating surface 306H supports the bearings 312 when placed inthe recess as shown in FIG. 9B. As can be realized, bearing 312 iscapable of supporting both axial and radial loads. Suitable examples ofultra-thin bearings for use with this exemplary embodiment are availablefrom Dynaroll Corp. (for example Dynaroll Application No. B4-72T12). Inalternate embodiments, any other suitable bearing may be used torotatably couple the chuck and base. In still other alternateembodiments, the chuck may be rotatably coupled to the base by any othersuitable means such as for example magnetic coupling.

Still referring to FIG. 9B, the raised inner portion 307 (compared toouter channel 308) has a pocket 307P in this embodiment for mountingsensor 317 for the positional resolver 316 of the end effector. The PCBsection 302F may include suitable conductive traces (not shown) formedintegrally into the PCB for connecting the sensor 317 to the controller10. Otherwise, conductors 317C may be connected to the sensor 317 andextend over a surface of the PCB section to connect the sensor tocontroller 10 as shown for example in FIG. 10 The PCB section 302F mayinclude any other desired number of recesses or pockets (not shown)similar to openings 230, 232, 234, 236 in FIG. 7 for receiving sensorssimilar to sensors 240, 242, 244, and 246 that are positioned around theperipheral portion of the end-effector base for sensing the position andorientation of the substrate.

Referring now to FIGS. 9, 9A-9B and 10, the chuck 322 may include astructure member 324, as well as the motor rotor 314 and a portion ofthe positional resolver 316, connected together as a one-piece assemblyas will be described further below. The chuck structure member 324 maybe a one-piece member or may be an assembly as desired to reduce weightof the end effector as well as weight on the PCB section 312F. The chuckstructure member 324 may be made from stiff light weight materials suchas composites. The structure member 324 may be substantially flat asshown or may have any other suitable configuration. The upper surface324U has a suitable substrate support structure 326. The supportstructure 326 is configured to effect edge-gripping of the substrate S.In this embodiment, the support structure 326 comprises pads 326P (fourare shown for example purposes) raised from the upper surface 324U. Thepads 326P are arranged to contact the perimeter edge of the substrate(see FIG. 9). When the substrate is picked with the end effector, thesubstrate is seated on the pads 326P and a gap is formed as shown inFIG. 9B between the substrate S and upper surface 324U of the chuck. Inalternate embodiments, one or more pads may be provided that are movable(such as by pneumatic or electro-magnetic means) to engage the edge ofthe substrate and grip the substrate between the pads. In thisembodiment, the PCB section 302F may be provided with a vacuum source(not shown) similar to vacuum port 224 and seal ring 226 (see FIG. 7)for securing the substrate S to the chuck.

As noted before, the chuck 322 holds the motor rotor 314 as well as aportion of the positional resolver. As shown in FIG. 9B, the lowersurface of the chuck support member 324 has a number of pockets orrecesses 328, 330, 332 formed therein. The recesses are also indicatedby dashed lines in FIG. 9. Recess 328 is sized to receive the permanentmagnets 314A, 314B forming the motor rotor 314. Referring again to FIG.12, the rotor 314 in this embodiment may be formed from a set ofpermanent magnets 314A, 314B arranged with alternating polarity asshown. The magnets may have any suitable shape (and are shown as havinga circular shape for example purposes only). As can be understood fromFIGS. 9B and 12, the recesses 328 receiving magnets 314A, 314B areshaped to conform to the magnets. The magnets may be mounted or bondedin the recesses with any suitable potting compound, adhesive, or anyother suitable means. In alternate embodiments, the rotor magnets may beattached to the lower surface of the chuck without nesting in pockets orrecesses. As seen in FIG. 12, the rotor magnets 314A, 314B are arrangedto operably cooperate with the stator windings 310A-310C in the PCBsection 302F when the chuck is mounted on the base. Further, the magnetsare so arranged that the axis of rotation R of the motor 309 extendssubstantially through the center C of the substrate S when seated onsupport structure 326 of the chuck (see FIG. 8).

As noted before, in this embodiment the chuck 322 is positionallycoupled to the base by bearing 312. Recess 332 in the lower surface ofthe chuck (see FIG. 9B) is sized to conformally receive the bearing 312.Correspondingly, recess 332 may have an annular shape, forming an innerradial bearing surface 332R and a horizontal seating surface 332H. Asseen in FIG. 9B, when received in recess 332, the bearing 312 bears withthe inner face against radial surface 332R and is seated on the upperface on seating surface 332H. Thus, bearing 312 provides the positionalalignment between the motor rotor 314 in the chuck 322 and the motorstator 310 integral to the PCB section of the base 302 of the endeffector. As seen best in FIG. 9B, bearing 312 maintains a clearance gapbetween chuck 322 and PCB section 302F when the two are coupled. In theembodiment shown in FIG. 9B, the recess 330 of the chuck receives thepositional encoder 315 of the positional resolver 316 (see also FIG. 8).As can be realized, motor 309 in this embodiment is rotary, and hencethe positional resolver may be a rotary resolver using an encoder ring.In embodiments where the motor is linear or planar, a linear or planarresolver may be used. The resolver 316 may be any suitable type ofresolver, such as an optical resolver or electromagnetic resolver. Inthe case of an optical resolver, the sensor 317 in the base, may be anysuitable optical sensor (e.g. Photo cell, CCD, laser). The encoder ring315 may have any suitable optically readable indicia. In the case of anelectromagnetic resolver, the sensor may be a capacitive sensor, and theencoder may have magnetic indicia/features so that the output from thecapacitive sensor provides indications of the position/orientation ofthe chuck relative to the base. In other alternate embodiments, thesensor of the resolver may be integrated into the windings of the statorso that positional resolution of the rotor may be provided to thecontroller by stator feedback. The controller 10 uses the informationfrom the rotary resolver for commutating the windings of the motor 309to effect motion of the chuck 322, and hence the substrate S on thechuck, relative to the base.

Motor 309 may be controlled by controller 10 to orient the substrate S“on the fly” in a manner substantially similar to that described beforewith reference to the embodiment shown in FIG. 7. For example, afterpicking a substrate S, the controller may operate motor 309 to rotatethe chuck in a desired direction (e.g. clockwise or counter-clockwiseabout axis R) until the fiducial (notch, see FIG. 5) on the substrate isdetected by a sensor (similar to sensors 240, 242, 244 in FIG. 7). Thecontroller may use information from the sensor to generate orientingsignals for motor 309. This causes the end effector to rotate about axisR (see FIG. 8) until the substrate S is in a desired position relativeto the end effector. In this position, however, the chuck 322 of the endeffector may be out of true with the sides of the end effector base 302.The chuck 322 is shown in this out of true position in FIG. 11. The basemay be provided with suitable elevatable supports 350, if desired toallow resetting the chuck 322 while maintaining the substrateorientation. The elevatable supports may be of any suitable type,including for example, piezo-electric, pneumatically actuated or anyothers. In FIG. 11, four elevatable supports 350 are shown for examplepurposes only. The supports 350 are located on the base 302 of the endeffector to contact the perimeter edge of the substrate S. As can beseen in FIG. 11, the supports may be raised or elevated from the uppersurface of the base 302 (in the direction indicated by arrow Z in FIG.11) to lift the substrate from support structure 326 of the chuck. Thesubstrate is seated on raised supports 350 while the chuck is resetusing motor 309 to a true position (see FIG. 8). The supports 350 maythen be lowered to place the substrate S again on the chuck supports326. The orientation of the substrate S is thus maintained while thechuck position is reset.

The end effector 300 in accordance with this exemplary embodimentprovides numerous advantages over conventional systems. Incorporating,by way of example, the motor stator windings into the end effector base,which is a PCB of unitary construction, reduces overall weight of theend effector as well as minimizing profile height. In addition, the baseis provided with higher stiffness by avoiding large cutouts in the basestructure for inserting the motor. Further advantages, for examplefurther reduction in end effector profile, are achieved by placement ofthe rotor in the chuck. The “on-axis” position of the motor eliminatesuse of a transmission thereby further eliminating weight, complexity,and cost compared to conventional systems.

It will be apparent to those skilled in the art that other modificationsto and variations of the above-described techniques are possible withoutdeparting from the inventive concepts disclosed herein. Accordingly, theinvention should be viewed as limited solely by the scope and spirit ofthe appended claims.

1. A substrate transport apparatus comprising: a movable transport arm;and an end effector movably connected to the transport arm, the endeffector having a chuck adapted for holding a substrate, and a motor formoving the substrate held by the chuck, wherein the motor is disposedrelative to the chuck so that, when the substrate is held by the chuck,a center of the substrate is substantially co-incident with an axis ofmovement of the motor.
 2. The apparatus according to claim 1, whereinthe end effector has at least one sensor thereon to sense anpredetermined characteristic of the substrate.
 3. The apparatusaccording to claim 2, wherein the predetermined characteristic is atleast one of an edge of the substrate or a fiducial feature of thesubstrate.
 4. The apparatus according to claim 2, further comprising acontroller in communication with the at least one sensor and the motor,and wherein the controller is programmed to actuate the motor for movingthe substrate based on information from the at least one sensor.
 5. Theapparatus according to claim 4, wherein the controller is programmed tomove the substrate with the motor substantially simultaneously with thetransport arm moving the substrate from one station to another station.6. The apparatus according to claim 1, wherein the end effector has asupport member supporting the chuck, the chuck being rotatably mountedrelative to the support member to rotate relative to the support member,and wherein the axis of movement is an axis of rotation of the motor. 7.The apparatus according to claim 1, wherein the chuck is adapted foredge gripping the substrate.
 8. The apparatus according to claim 1,wherein the motor is a brushless motor and is located on a supportmember of the end effector supporting the chuck, the brushless motorbeing located on the support member at a location under the chuck. 9.The apparatus according to claim 8, further comprising a positionalresolver connected to the chuck for providing position information ofthe chuck to a controller operating the motor.
 10. The apparatusaccording to claim 1, wherein the motor comprises a stator and a rotor,the stator being integral to a base of the end effector, and the rotorbeing integral to the chuck.
 11. A vacuum substrate processing systemcomprising the apparatus according to claim
 1. 12. A substrate transportapparatus comprising: a movable transport arm; and an end effectormovably connected to the transport arm and being adapted for holding asubstrate thereon, the end effector comprising a PCB, the PCB forming atleast part of a support member of the end effector for supporting thesubstrate when the substrate is held by the end effector.
 13. Theapparatus according to claim 12, wherein the PCB comprises at least partof a motor for moving the substrate on the end effector relative to thetransport arm.
 14. The apparatus according to claim 12, wherein a faceof the PCB extends along at least a portion of a face of the substratewhen the substrate is held by the end effector.
 15. The apparatusaccording to claim 12, wherein the PCB has conductive traces formedtherein defining windings for a motor stator.
 16. The apparatusaccording to claim 15, wherein the motor stator is for a motor effectingmovement of a chuck of the end effector.
 17. The apparatus according toclaim 12, wherein the end effector has a chuck for holding the substrateon the end effector, the chuck resting on the PCB.
 18. The apparatusaccording to claim 12, wherein the end effector has at least one sensorthereon to sense an predetermined characteristic of the substrate. 19.The apparatus according to claim 18, wherein the PCB has integralwindings formed therein defining at least a portion of a motor formoving the substrate on the end effector, and wherein the motor isoperated by a controller using information from the at least one sensor.20. A substrate transport apparatus comprising: a movable transport arm;an end effector movably connected to the transport arm, the end effectorhaving-a base section mounting the end effector to the transport arm,and a chuck movably mounted to the base section and adapted for holdinga substrate; and a motor connected to the end effector for moving thesubstrate held by the chuck, wherein the motor is integral with the endeffector, at least a drive part of the motor being mounted to the basesection of the end effector and at least a reaction part of the motorbeing mounted to the chuck.
 21. The apparatus according to claim 20,wherein the drive part is a stator and the reaction part is a rotor, andwherein the stator is disposed on the base section and the rotor on thechuck so that, when the substrate is held by the chuck, a center of thesubstrate is substantially co-incident with an axis of rotation of themotor.
 22. The apparatus according to claim 20, wherein the motor is abrushless motor.
 23. An end effector motor for an end effector of asubstrate transport apparatus, the end effector having a support memberand a chuck movably mounted to the support member and adapted forholding a substrate thereon, the motor comprising: a stator sized andshaped for being embedded in the support member; and a rotor operablyinterfacing with the stator and adapted to be mounted to the chuck ofthe end effector.
 24. The motor according to claim 23, wherein thestator comprises windings formed on a PCB.
 25. The motor according toclaim 24, wherein the PCB is integral with the support member of the endeffector.
 26. The motor according to claim 23, wherein the rotorcomprises at least one permanent magnet.
 27. The motor according toclaim 23, further comprising a rotary resolver connected to the rotor,and a controller communicably connected with the rotary resolver and thestator for commutating windings of the stator.
 28. A substrate transportapparatus comprising: a movable transport arm; and an end effectormovably connected to the transport arm, the end effector comprising asupport member mounting the end effector to the transport arm, a chuckmovably mounted to the support member and adapted for holding asubstrate, and a motor for moving the substrate held by the chuck,wherein the support member has a portion of unitary construction thatdefines a stator of the motor.
 29. The apparatus according to claim 28,wherein the chuck is mounted to the portion of unitary construction ofthe support member.
 30. The apparatus according to claim 28, wherein theportion of unitary construction extends under the chuck.
 31. Theapparatus according to claim 28, wherein the motor comprises a rotor,the rotor being mounted to the chuck.
 32. The apparatus according toclaim 31, wherein the rotor comprises permanent magnets.
 33. Theapparatus according to claim 28, wherein the motor is a brushless motor.